Hmm, I may have some gasket matching to do..... I finally digitized and scaled the port imprints I made and the ports are smaller than the valve area.... By a lot. I guess that'd be a problem with an over sized valved engine? Before I opened up the area behind the valves it was right about the same cross sectional area as the port, though I didn't know the port area then.

Also, despite the odd shape of the #1 and #6 exhaust ports their area is comparable to the other exhaust ports (at least after I opened up #6 yesterday) The average area of the intake ports were 2.34 sq inches and the average of exhaust ports 2-5 was 1.82 sq inches and 1&6 1.85 sq. inches.

So I guess I can stick the gasket on the head and gut out the head and taper into the port? Then reverse into the intake, though I cannot reach very far into the intake, especially where the runner curves. Live and learn I suppose, I didn't expect this problem. Though I'm sure the cross sectional area is still pinched down some a bit before the backside of the valve, where the valve guide sticks into the port.

Edited by TheSilverBuick (06/19/1410:33 AM)

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

You can see where the exhaust manifold flange overhangs the ports on the head, this should probably be opened up to the port opening in the head also. This can cause a restriction for outgoing exhaust and can help exhaust breathing.

I know exactly what you mean about wide spotting it at the gasket surface. Porting mistake #1, and why I did not touch the gasket side of the port outside of smoothing casting bumps. But now knowing the port's cross sectional area (2.34 sqin)is less than that of the intake valve minus stem (2.80 sqin), and the area from seat to valve at full lift is 2.64 sqin, the air is going to slow down from the gasket surface to the valve if I do nothing. So if I at least taper the port to the gasket now, and make a good showing of it on the stock intake manifold, it'll set me up well for the sheet metal intake, though the sheet metal intake is for the turbo engine, I expect the ports to be cleaned up to the standard gasket size.

Worse case the runners from the sheet metal intake have to be re-done, and I hardly expect to make a great intake on the first try, so may as well get a practice one in that can taper properly from plenum to valve.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

When the machinist looked at the head his opinion was that the head has had some work done to it in the past. He said that the intake guides had been replaced with new iron guides and it looked like the head had been surfaced before. So he ground the valves and seats to a fresh 45* angle, pulled 0.030" off the bottom and a bit off the side to flush up the intake divider. In a mis-communication he cut down the exhaust valve guides so valve guide seals could be installed on the exhaust. Oh well, it's nice work The block had 0.035" shaved off the top, which should leave the pistons 0.003" in the hole if my measurements were good. I'm going to re-measure it when I have the short block back together, but crunching all the numbers now takes the compression from 8.02 to 8.58. I only lost 1cc from before my chamber work and cutting the head, from 76 to 75. I measured out the port lengths as well and was shocked at how consistent the were. All measurements port to port only varied by a 1/16" which is likely the margin of error of how I was measuring them (with a wire). Averaging the top and bottom measurements the intakes were 3.125" long and the exhaust were 3.063". I think it will want an 8" runner on the intake manifold for an 11" induction length.

So it turns out there is not a whole lot to do for the intake ports, and a bit to do for the exhaust ports. It looked like the

The intakes against the two gasket types I have.

The exhaust against the two gasket types I have.

The valves were re-ground. The stock 45* seat angle. The black marks are just sharpie marks.

The head with the cc's written on it.

I finished all the metal work on the short block. Got 0.035" shaved off the deck and flexball honed the cylinders. I tapped all the spots where the baffles were riveted in with 1/4-20 threads so I can bolt the baffles back in after I add more baffling behind them. I've hosed off the block inside and out and dried it out with compressed air and fogged the cylinders and deck with WD-40. I'll probably re-paint it either tomorrow or during the week. For now I have it bagged and sealed.

Tomorrow I'll work on the last bit of head work, get the head cleaned all up and possibly re-assemble it, with the new valve springs. Get the pistons cleaned up and install the new rings. Work the over the baffling and re-install them. Finish working over the intake and exhaust manifold ports with the die-grinder and if I get really really ambitious I'll get the cylinders real cleaned out and install the crank and pistons. I need to shorten the head dowels and make sure the head bolts don't bottom out.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

When opening up the exhaust ports, don't spend a bunch of time on the bottoms of ports. Concentrate on the tops of ports. Very little flow in the bottoms, infact, you can hurt flow by opening the bottoms. Keep up the good work.

The margins aren't that wide on the head, maybe about .05", seemed like a standard contact width to me. It's a single angle cut, ran out of time to do a multi-angle job. The machinist really wanted to do a 3-angle job on them, but between the rough shape of the valves and the time limitation I imposed on him, he was limited to a stock single 45* cut. Three of the intake valves he absolutely did not like the look of, but new valves are either pricey NOS or full custom, and I already have spent more than I wanted too plus again the time constraint.

The guides on the intakes apparently had been replaced before and he said he didn't see any reason to replace any of the guides and that I was using the wrong type of valve stem seal on the intakes.

I'm going to make the sheet metal intake on this engine so I can be sure it clear's everything like the wiper motor. I am changing up how I was going about it though, originally I was going to use simple exhaust tubing, but now I'm going to take a 2x4 and shave it down with the proper taper and bend and hammer sheet metal around it. It should get me a consistently shaped runner that is rectangular like the port. My air flow buddy is ready to make me an aluminum intake, but had to tell him he was putting the cart before the horse because I need to know it clears everything. So I may take him up on his offer when I have a functional intake that clears everything and ready to spend the money.

I agree with you Tom on the exhaust ports, I'm not going to go all out on the bottoms.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

Not at the rate of work I did today =P The only thing I did today was make the baffles and touch up the paint on the block =P I'm hoping the baffles help as I've done no research on effective baffling. The 1/4-20 screws are loc-tite'd in.

This is the stock oil fill tube baffle. It's easy to see the light where the oil fill tube goes. This is also the side of the block the crankshaft slings oil upwards.

So I riveted some sheet metal to it to try and trap the slinged oil and let it run down the sides. I was holding it upside down in the picture, so I rotated the picture. I had to notch it afterwards because of interference with the oil dipstick, so it got a bit rough on that side.

In place and no more light seen. Then from the top, when adding oil, it should hit the baffle at the top and run down the sides.

The stock baffling on the PCV port. The light is the hole for the PCV tube.

This one I really wasn't certain what to do for it, so I just made some air flow interrupters that I hope cause the oil to drop out. Most the air should change directions at least twice before making it to the port.

The baffles push up against the block, mostly sealing against it, so again most the air will change directions twice before getting to the port, hopefully dropping oil along the way. The shiny brass fitting there is a port I added to measure the crankcase vacuum/pressure. I'll have it hooked to a vacuum/boost gauge and maybe someday to the megasquirt as something to datalog.

I'll shoot for next Friday. I need to clean and install the pistons/bottom end. Do the last bit of port work on the head then clean and assemble it. Clean up the intake and exhaust manifolds. Lengthen the wiring harness ~8 inches or so. I'm going to try and accomplish one of those each day after work. So hopefully I'm ready for install on Friday, Saturday at the latest. I still have to replace the rear fuel filter as well.

Edited by TheSilverBuick (06/22/1402:54 PM)

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

Summer softball league has started and tied me up a few times now. I finished porting out the head as far as I'm going to take it as well as the exhaust and intake manifold. I cleaned the carbon off the pistons as well.

Tonight I plan to clean up the intake, exhaust and head to paint first thing tomorrow morning as well as install the new piston rings on the pistons and fully assemble the head. The paint can dry while I start assembly of the bottom end. Hopefully I will have the engine together by the end of tomorrow and go to set it in the car on Saturday. I still need to lengthen the wiring harness so perhaps I'll do that tomorrow night.

I'm contemplating running all new fuel lines in the car from the back of the car to the engine bay. Move the fuel lines to the driver's side and move the high pressure fuel pump more rear wards, with the fuel pressure regulator and such all at the rear of the car and run a single fuel line to the front. I don't currently have a pass through fuel rail and it seems to be working fine.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

I measured the ring gap this morning and found some interesting numbers. Measured it 1.5" from the top and measured it 4" from the top (3.53" stroke) and the taper changed the gaps about .0025". I didn't back calculate what the bore diameter difference was. BUT the big difference is between the old and new rings, or at least the one of each I checked. The old ring had a gap of .055" at the bottom of the cylinder and .057" at the top of the cylinder where as the new ring had .0185" at the bottom and .021" at the top. That is a huge difference. Doing the calcs for the 3.905" bore, at .004" per inch of bore for N/A applications, .0156" is the minimum gap recommended, and using .006" per inch for boosted applications I get .0234" for a minimum, so .021" will probably get me by if I put a turbo on this engine because the cast pistons will probably require keeping the boost down anyways. I pulled the recommended gap numbers from the Mahle website, whom the rings are made by.

The tighter ring gap ought to help out in the compression and blow-by departments.

Stuck the pistons in it and retouched up the paint on the intake and exhaust manifolds as well as the head. I cleaned up the oil pan and will re-paint it tomorrow as well as touch up the paint on the other stuff. Tomorrow I'll assemble the head and start the final assembly of the engine.

Still some ragged looking pistons, but hopefully bumping the compression up a half point or so, theoretically improving air flow in the head and tightening up the piston ring gaps net me some gains in horsepower and reduce overall oil consumption.

Pistons all in and oil pickup installed.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

I have a big block Buick for quicker. Though if my turbo engine plans pan out the six will eventually surpass the Buick. For now I'll just take what I can get and the 4.56 gears for a bit more "fun".

Got the engine all together now. I need to put oil in and prime the system up still as well as install the fuel rail and throttle body. I found a couple of the upper injector o-rings cut or shaved, so I need to do some work on the fuel rail and further round out the entrance to the injector. The #4 injector that gave me the most problems was the worse. Eventually I got it so none of them leaked while running and driving, heck even held 20psi after the engine was shut off, but intermittently I'd have issues. I only had two new o-rings so I need to get a box of them tomorrow from NAPA.

I set the timing belt in place and if my math holds between the thicker head gasket and then shaving the head and block deck the cam is 0.045" closer to the crank and would retard the cam timing by approximately 2*, which is what I saw when I tightened everything down. I reset it from 2* retarded to 4* advanced.

I brought the wiring harness in the house. I'm going to set my card table up tonight with the soldering iron and lengthen the harness by about 8" while watching a movie so the plugs clear the back of the head.

I did more work after I took the pictures, the balancer and trigger wheel are on it now, as the cam timing isn't set in these pictures because I don't have the TDC mark that is on the balancer.

You can see the brass fitting I added below the red PVC tube that I'm going to hook a vacuum/boost gauge too to read the crankcase pressure. I may eventually hook a MAP sensor to it and datalog it with the MegaSquirt.

I touched up the paint on the belt cover as well.

Edited by TheSilverBuick (06/28/1407:06 PM)

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

Thanks. Yup, a Ford 2-wire IAC. Takes filtered air and sticks it right into the intake. Doesn't seem to work as well as the 4-wire IAC on my Skylark, it only seems to have 50% of the range it should have. I think I may have some setting goofed but haven't figured out what yet. It works good enough to get high idle when cold and does minimal work when the MegaSquirt is modifing ignition timing to target idle rpm.

That fuel pressure regulator is the external oil pressure regular to the lash adjuster galley. The hose going to the oil fill tube is the by pass line. While testing I reduced the feed line to 1/8" while maintaining a 3/8" drain to let it keep better pressure control and minimize oil bleed off the pump.

Not sure what there will be to adjust with the tune based on crankcase pressure.

I didn't measure the piston wall clearance.

I just finished lengthening the wiring harness so that is ready to go.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

Got the engine in, bolted up the transmission, torque converter, etc. Finished all work under the car, which was my main goal today. Tomorrow I plan to install the alternator and radiator and probably hook up the fuel line and throttlebody. I forgot I need to replace the rear fuel filter at minimum and see if that was the fuel starvation issue. Then it will probably be Wednesday before I change the fuel filter, but then should be good to fire it up.

All set in. I wrapped the wiring harness in friction tape and it compacts down much nicer and fits between the fuel rail and cam housing now.

I spent a couple hours last night adding about ten inches or so to the wiring harness. About 30 wires, two solder joints and shrink wrapping each, it took a while. But now the connectors are very easy to access and currently are behind the transmission dipstick. They are just sitting there but I might try and get them clamped to the firewall some how. Before one plugged in right behind the head and it was a pain to reach. I was quite happy with how easily the harness plugged in . There are three plugs and four ground terminals.

Edited by TheSilverBuick (06/29/1404:58 PM)

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

It certainly isn't any harder. Being tucked up against the firewall has it's own challenges associated with it when trying to get the transmission bolted up.

A late 80's Ford fuel pump. It's currently mounted to the floor pan under the passenger's feet and it's easy to hear in the car, so I want to relocate it and the surge tank to the rear but I have not yet done it. I did purchase the steel tubing to make new fuel lines though. I want to get it up and running then plumb the new lines into place while still being able to drive it, then spend a day/afternoon moving the pump, regulator and surge tank to the back of the car. Minimize down time.

The injectors are 32 lb/hr. They are hand-me-down's from my Skylark when I upgraded it to 44 lb/hr when I got to the fringe of the 32's abilities. For the six, they should do quite well naturally aspirated and get me a few pounds of boost with a turbo. It might get me to 10-12 psi, but I'll really be watching the AFR (and EGT's?) if I haven't upgraded at that point.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

For a while I used the stock 30LB injectors on my 4.3 V-6 & 21 psi, I ran out of injector, switched to 36 lb & running up to 25 psi & spraying methanol. Injectors still too small. But it's sort of a good thing the heads are restrictive flowing 150 CFM w/a 1.94" intake.

Nothing fancy, a ~6 inch piece of 3/4" box tubing with four nipples welded to the side of it. The high pressure pump pick up is at the bottom and return to the gas tank at the very top, with the regulator return second from bottom and the lift pump inlet second from top. That way any air the lift pump sucks up when the pickup is uncovered when low on fuel goes to the top and is returned to the gas tank, and the lowest outlet is always covered in fuel for the high pressure pump.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

Cooling and charging systems installed. I could probably fire it up right now, but to be safe I want to change the rear fuel filter and do a crank test with a timing light to make sure I don't have the cam sensor 180º out. It should be fine, but I rather check it. I have a softball game to go play now otherwise I'd be doing some of this work now.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

Fired the car up! And it was mostly good. Fired right up and idles well. I was getting noise out of the cam housing around cylinders 1 and 2, but it quieted up after a while so I think it just had air or something in the lash adjuster that needed to work itself out. I may need to adjust the oil pressure regulator. I'll be listening for it's return or any changes.

The other issue is it won't rev above 1,200rpm. The tach signal keeps dropping out. I re-adjusted the crank sensor and tightened up the clearances to the crank trigger, but it didn't change anything. I did a data log and all the inputs are reading clean, including the tach signal until it drops out. Tomorrow I'll adjust the tach signal filter pots on the MegaSquirt board and see if that clears it up. The crank and cam trigger signal log while cranking and idling are mint and clean, so its very likely to be the signal filter. Maybe that ~10" of wire I added was just enough to hiccup the signal?

But otherwise, I did get to hear it run and it fires up easy =D

Just going to get the tach signal sorted out, put the hood on and this weekend start on re-plumbing the fuel system.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

I had the vacuum pump turned on, and I thought about hooking up the vacuum/boost gauge (I just have the port capped at the moment) to check it out, but decided I'd wait until I was happy with the running of the engine (aka run above 1,200rpm). I'm 90% sure it's the signal filter adjustment.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

Got it nailed down to the pull-up circuit on the crank trigger has something goofy going on. In my experience when it's not hooked up I get no rpm signal, but in testing with a jumper circuit I got it revving up just fine. It sounds good. Now I have to go and actually repair it.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

Yup, looks like the solder joint in my after thought pull-up circuit resistor broke. Soldered back on, put it all back together and it's mint. Runs and sounds good. I put the hood back on and going to run to the hardware store for some odds and ends since they are not going to be open tomorrow then I'll wash the car and take a video or two.

The culprit.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

Got a video, but almost didn't. The dang fuel problem cropped up again and stranded me on the side of the road three times before I got it back home. I richened it up quite a bit, probably from unknowingly at the time offsetting the fuel starvation issue, so I need to un-do those changes. I'm going to drop the fuel tank tomorrow and check out the pickup and start redoing the whole fuel system.

Overhauled the fuel system. This should put an end to the fuel starvation issue for sure. I pulled the tank, and it is clean inside. I'm sure it's been replaced at some point in the car's past and the sending unit is certainly an aftermarket unit. The sock was black but relatively clean, but I removed it entirely anyways like I did on my Skylark. I moved the lift pump to the same level as the bottom of the gas tank (from the middle) and if that doesn't solve the issue, then it's the pump itself.

Made some pretty big changes by moving the pressure pump and surge tank to the rear of the car as well as all new fuel line on the driver's side (opposite side of the exhaust system and side the fuel rail is on). Despite not having a return line from the fuel rail it fires up quickly and so far runs pretty good. For reference, I've never had a return line from the fuel rail on this car. On to the pictures.

Here is the panel I made with all the fueling stuff on it. The lift pump on the bottom to the first filter, into the surge tank, then from the surge tank to the high pressure pump, through an EFI fuel filter, to the fuel pressure regulator then out to the front of the car or returned to the surge tank.

Mounted in the car. I utilized the lip on the gas tank as a support then two bolts through the trunk floor to secure it in place.

It's angled in place.

From the rear of the car. This union is my weeper. Just the top half, and it's the pipe that connects to the fuel pressure regulator. So I'll re-do the top half tomorrow.

Just following the brake line.

Along the outside of the subframe. Like OE, but on the driver's side.

Up into the engine bay. Ahead of the flywheel plane and a short piece of nylon fuel line to account for vibration.

My electric smog pump/crank case evacuation pump started blowing fuses, aka failing, so I swapped it out yesterday. I ammetered it and the old one was pulling 18amps when it was working (blowing a 25amp fuse) and the newly installed one is pulling 10 amps. I'm going to CA this weekend and going to hit a junkyard and see about pulling a mid-90's Ford Taurus electric smog pump as I've heard reports they have longer durability. Though the pump I removed had quite a bit of oil in it, so hopefully with the baffling I did there is less oil pulled into this one and longer service life.

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo

I tried to drive the car to southern California, and I was barely 30 minutes outside of town when it lost fuel pressure. I went under the car and by pinching the return line to the fuel tank (not the regulator return line) the pressure would come right back. Let go and pressure would go away.

Early troubleshooting actually made it seem like a pump cavitation issue, particularly with the lift pump. I had installed a higher pressure TBI pump (~22psi) for my lift pump when the universal one quit working. So I put a clamp on the fuel line and motor'd on. It hiccupped a couple times then I got a solid 80+ mile stretch without issue and thought I had it kicked, but then it cropped up again. So 155 miles into my 475 mile drive south I opted to turn around and head home, which it drove the 155 miles home without a single issue, ARRRGGHHH! My girlfriend is accusing the car of being a homebody, lol.

So at that point, I figured it was a cavitation issue and the TBI pump needed some pressure to push against, so I made a restrictor tube from a piece of steel tubing with a 1/4" chunk of barbed brass fitting in the middle and installed it in the middle of the fuel tank return line, and the next day I drove out to Bonneville for a day trip test drive. It's ~130-140 miles each way and it was due to be 97ºF there to test for heat (and it was hot!), as it doesn't quite get warm enough here for proper testing. Well I made it out there, purr'ing like a kitten, drove to the end of the road at the Salt Flats, went back ate lunch, then as I was heading home I didn't even make it out of Wendover before it lost fuel pressure again. This time I tried pinching the lines and it wasn't coming back. So it is likely a vapor lock issue of some sort and my restrictor tube made it so when it vapor locks it vapor locks hard. Frick.

So the suggestions were to re-do the fuel system again to a "best practices" set up with the regulator at the end of the fuel rail and the return all the way back. In my mind though, I cannot see how this will make the fuel stay cooler as it would then take heat picked up in the fuel rail and bring it back to the tank as well as if I use the OE fuel line it crosses within and inch of the exhaust at the rear of the car to pick up more heat.

So I made two changes to the existing system. The first is I welded together a larger surge tank. Similar design but almost twice as tall. I put the high pressure pickup at the bottom with around 4" of distance before the next inlet. I've ran the inlet for the lift pump next inline, so the return from the regulator is above the lift pump inlet to try and push the returned fuel upwards and back towards the fuel tank return. Then I welded three "cooling" fins to the side of it. They hang off the side of the panel, past the gas tank and should pickup quite a bit of airflow. Theoretically helping cool the fuel in the surge tank. Then the other change I made was I installed a low pressure lift pump (essentially the same model pump that was on it to begin with) to reduce the pressure loading of the fuel (though I don't think 22psi adds much compressive heat).

The OHC purred like a kitten, still appears to be getting around 20mpg, oil pressure while cruising is now with 10w-40 oil is at the regulator spring limit of 55-60psi. It gets a little warmer than I'd like, but coolant temps didn't crest 195ºF and that is livable. The front crank seal appears to be leaking some oil, it doesn't have the blow by it had before (doesn't puff smoke out the oil fill tube with the cap off), the evac pump still pulls a fair amount of oil, so the baffles haven't changed a whole lot and I probably still need to work on getting the oil cap and dipstick tube sealed.

The smoke from the wild fires in Washington made the salt flats too hazy for a really great picture.

Edited by TheSilverBuick (07/21/1409:09 AM)

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Rebuilding an OHC Pontiac 250 with EFI and a Turbo